### What changes were proposed in this pull request?

- Correctly release `ByteBuf` in `TransportCipher` in all cases
- Move closing / releasing logic to `handlerRemoved(...)` so we are guaranteed that is always called.
- Correctly release `frameBuf` it is not null when the handler is removed (and so also when the channel becomes inactive)

### Why are the changes needed?

We need to carefully manage the ownership / lifecycle of `ByteBuf` instances so we don't leak any of these. We did not correctly do this in all cases:
 - when end up in invalid cipher state.
 - when partial data was received and the channel is closed before the full frame is decoded

Fixes https://github.com/netty/netty/issues/9784.

### Does this PR introduce any user-facing change?

No.

### How was this patch tested?

Pass the newly added UTs.

Closes #26609 from normanmaurer/fix_leaks.

Authored-by: Norman Maurer <norman_maurer@apple.com>
Signed-off-by: Marcelo Vanzin <vanzin@cloudera.com>